To assess this race between animals and the elements, scientists looked at climate records from the past 300,000 years, a period that included three ice ages. And they asked how a particular organism, the North American rattlesnake, coped with those climate changes.

They found that rattlesnakes, which are cold-blooded, deal with temperature changes by moving: their ranges have shifted about two meters a year to keep the snakes inside their comfort zone. Now, if global temperatures increase by another 1 to 6 degrees Celsius over the next 90 years, as current models predict, rattlers could be forced to slither up to a thousand times farther. And the snakes may not have the legs for such a trip.

How millions of other species will attempt to cope is a vast, unplanned evolutionary experiment. With no control in sight.